Mitsubishi Electric Melsec QJ71LP21 Reference Manual page 77

3 SPECIFICATIONS
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REMARKS
If the network module has become faulty, a loopback may not be made depending
on the fault. In this case, the data link may become deactivated. Identify the faulty
network module in the following method.
(1) Check the LED indications (RUN LED off, ERR. LED on) of all network modules
for a faulty station.
(2) Turn off the power to all stations, then turn it on in order from the control station.
In this process, check to which station of the network loopback is properly
executed.
Confirm in the Link information of the Network diagnostics (Host information)
screen that the control station and the normal station returned to the network is
displayed as loopback stations. (Refer to Section 8.1.1.)
Replace any network module in which malfunction has been detected, and confirm
that the data link is properly recovered.
MELSEC-Q
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